How can I change the order of workspaces tabs?
Decide which order you want your workspaces in.
Right-click the first (leftmost) and select Reorder to Back.
Continue the same with the next (second leftmost) workspace and so forth.

When you're done Reorder to Back on every workspace, they'll appear in the order you wanted.
Tip: Instead of having to redo this whole process when you want to insert a new workspace: Right-click on the workspace you want to precede your new workspace and choose Duplicate.